What is your source of information ?
Monarch Airlines made a profit of £70,000 last year. Yes it is a profit but in Airline terms £70,000 is marginal. You could look at it that if Monarch had one more A330 captain, the airline would have not made a profit.
An airline with a turnover of over £600,000,000 that's only making a profit of £70,000 is not in a financial position to buy Jet2. Monarch would also have to buy Jet2Holidays and the numerous unknown trading names Jet2 have. That is a pretty hefty investment, and considering Jet2 is currently more profitable than Monarch, if anything The Dart Group would be looking at taking some sort of share in Monarch. There is no way the Dart Group is about to be dissolved and PM letting go of his baby.